Actuators of this type are generally adapted to automatically open and close a valve with a structure in which a motor-driving shaft provided inside the actuator and a valve stem are connected directly or through a clutch mechanism. During power breakdown or in case of emergency, however, manual operation to open and close the valve is required.
Manual operation has heretofore been performed through a method of attaching a separate, manually operating shaft to a clutch mechanism, a method of projecting a motor-driving shaft from the upper or lower part of an actuator cover and using a tool to manually operate the projecting part of the motor-driving shaft, or a method of forming a hole in a motor-driving shaft and a projection on a valve stem, or vice versa, and inserting a tool into the hole to perform manual operation (see JP-A SHO 60-16074 (UM) and JP-A SHO 61-177266 (UM), for example).
On the other hand, there is a case where a valve or an actuator is generally provided with a flange or tapping seat as means for mounting the actuator on and connecting it to the shaft-mounting portion of the valve, and the actuator and shaft-mounting portion are fastened to each other with bolts or other such means (see JP-A SHO 54-92437 (UM), for example).
However, the conventional manually operating mechanisms for electrically operated actuators are complicated in structure and are large-sized in overall shape, and the manual operation is generally made using a tool to deteriorate operability. Therefore, demand is raised for development of electrically operated actuators that can solve the aforementioned problems. Since holes for bolts formed in a flange of an actuator of this type or valve have a slightly larger diameter than the bolt outside diameter in view of a fitting tolerance in relation to the bolts, when the bolts are loosened in attaching the actuator to or detaching it from the valve, there is a possibility of the actuator being shift by the amount of a gap between the bolts and the bolt holes. This fails to securely maintain the completely closed state when a rotary valve is required to completely close, resulting in a malfunction of the valve. In addition, when the flange is to be tapped, this requires an additional tapping work and necessitates a space for rotating and loosening the bolts in attaching or detaching the actuator and an operation tool, such as a wrench, screwdriver or other such means. Therefore, demand is also raised at the same time for development of a fixing configuration in the electrically operated actuator that can solve these problems.
The present invention has been developed in view of this state of affairs, and its object is to inexpensively provide a compact, electrically operated actuator simple in structure, light in weight and safe in operation. Another object is to provide an electrically operated actuator attachable to and detachable from a rotary valve by a single operation, and a fixing configuration for the actuator. A further object is to provide a fixing configuration for firmly fixing an electrically operated actuator with the rotational direction and axial direction of a rotary valve restrained, and a compact fixing structure capable of firmly fixing an electrically operated actuator with ease and applicable also to mechanical parts.